Linux Format的September 2015目录

Jonni Bidwell Like many people, my first experience was writing in Basic on the classroom’s solitary BBC B. The function keys allowed you to colourise output, which added a new dimension to looping PRINT statements. Unfortunately the arguments to that command cannot be reproduced here. Neil Bothwick I started on a University mainframe using Algol68 and later I ‘progressed’ to Pascal, but at least I managed to avoid Fortran and Cobol, unlike some of my friends. This was a little while [eons? – Ed] ago, not only did we use punched cards, but our first program was Salve Mundus. Alex Campbell Fun fact for you: I started programming in high school in an Advanced Placement (AP) Computer Science class. We were learning how to code in C++ and I failed…

It looks like enough is enough for Adobe Flash, with the number of vulnerabilities that affect the troubled software causing several well known companies to ditch the technology. While “people hate Flash” isn’t really newsworthy, the fact that Mozilla has seen fit to block all versions of Flash by default in Firefox certainly is. Mark Schmidt, the head of Firefox’s support team at Mozilla, tweeted the news accompanied by an attention-grabbing image of a raised fist and the words “Occupy Flash”. This isn’t the first time Mozilla has blocked Flash, and it doesn’t mean it’s completely gone from Firefox, because users can always turn it on in the settings menu. Doing so may not be very prudent, though. Schmidt explained that “Flash is only blocked until Adobe releases a version…

LibreOffice 5.0 (actually the tenth version of the open-source office suite) has been launched, the first such release in its third development cycle. Building on the success of LibreOffice 4.x (which according to a Document Foundation estimate has been deployed to over 80 million users), LibreOffice 5.0 sports an improved user interface, with better management of screen space and a more pared-back and cleaner look. Better interoperability with office suites such as Microsoft Office and AppleiWorkis another benefit in the new version, with better support for non-standard formats. Perhaps most importantly of all, LibreOffice 5.0 has been cleaned up and improved with better stability and less old code cluttering the software up. This leads to better performance as well as less stress being put on the battery of laptops running…

PyConUK We eyeball the future of Python in the classroom. PyCon UK is one of the many PyCon events that take place around the world. The goal of the event is to further the use of Python in schools and industry, and at each PyCon there’s a growing trend of educators taking part and working with established Python developers to introduce the language into classrooms around the world. We saw this first hand at PyConUK in 2013, when the Raspberry Pi was still in its early days. Fusing Minecraft Pi, Python and a Parrot Drone developers and teachers quickly hacked a controllable drone that merged Python with physical computing. At PyConUK the team has successfully run an education track for the past four years that provides training for teachers on…

£4k review Before you go overboard in an UltraHD 4K craze, read this article about High-bandwidth Digital Content Protection (HDCP), the counterattack from the media content business. http://bit.ly/HDCPLowdown. HDCP 2.2 is the next generation of copy protection for the 4K era, and it likely won’t work with any of your current gear. Not only is it not backwards compatible, many new 4K devices don’t even support it. The current gear will most likely not be HDCP 2.2-upgradable either. The copy protection will most certainly be broken, just like all its predecessors. So why bother? It will present a hassle for all those people just trying to set up a new TV or connect other 4K equipment in a video/ audio chain that’s not compliant with HDCP 2.2. Before you shell…

Specs Name: i7-5775C Socket: 1150 Cache: 6MB Type: 64-bit SSE: SSE 4.1/4.2, AVX 2.0 Process: 14nm Cores: 4 Threads: 8 Clock: 3.3GHz Turbo: 3.7GHz TDP: 65W Max mem: 32GB DDR3 Channels: 2 GPU: Iris Pro 6200 Clock: 300MHz Max: 1.15GHz Units: 48 OpenGL: 4.3 Displays: 3 Virtual support: VT-x, VT-d, VT-x EPT Intel’s fifth-gen desktop CPU, the Core i7-5775C, is finally on our test bench. So hey there, Mr Broadwell, what took you so long? If you talk to anyone at Intel, they tell you the 14nm architecture was released in 2014. And yet we’ve only just got our hands on the first proper Broadwell processors. By ‘proper, we mean full-fat, quad-core desktop processors, with capable clockspeeds and overclocking potential. Technically, Broadwell was released in 2014. Well, some of it.…

You’d think that by now laptop manufacturers would have cracked the design of decent keyboards and touchpads for mobile devices, but you can never be too careful especially on value propositions like the average Chromebook. The Chromebook 15, for example, bends when you press the bottom strip of the touchpad. It’s nothing deal-breaking but it’s annoying as otherwise it’s a lovely MacBook-like oversized touchpad. The extra size is also taken up with a decent full-sized keyboard that’s missing only a number pad. At the opposite end of the size scale, the Acer Flip still squeezes in a full-size keyboard. Key travel feels deep despite the fact the keyboard sits on a recessed deck, which appears to leave less than 2mm of space between it and the bottom of the Chromebook.…

Coding is the new cool. If you don’t know how to Python, all your friends are going to be laughing at you… We’re not being flippant. Knowing how to code is almost an essential for the open source fiend. Be it basic Bash scripting or knowing how to read a bit of PHP, coding knowledge is more than useful, it’s an essential. With coding now being pushed at school, there’s never been a better time to brush up on your skills, so when little Jenny asks for help with Python hacking Minecraft on her Pi, you can dive right in without fear. Knowing a bit of code helps with using Linux itself, helps you get more out of the terminal, can open doors to a new career or help you…

Gomoku is short for gomokunarabe, which is roughly Japanese for ‘five pieces lined up. The game in fact originated in China some 4,000 years ago. Players take turns to each place a counter on the intersections of a square grid with the goal of forming unbroken lines (horizontal, vertical or diagonal) of length 5. Traditionally the board has 19x19 intersections, but we’ve gone for the smaller 15x15 board used in some variations. We haven’t included an AI (that would be somewhat too complicated for a beginner tutorial) so you’ll need to find a friend/other personality with which to play. Alternatively there are plenty of online versions you can play, and KDE users get the similar Bovu game with their desktop. It’s easy to figure out some basic strategies, such as…

With imperative programming the order of execution is largely fixed, so that everything happens sequentially. Our Gomoku example is done largely imperative style, but our use of functions makes it more procedural – execution will jump between functions, but there is still a consistent flow. The object oriented (OO) approach extends this even further. OO programs define classes, which can be instantiated many times; each class is a template for an object, which can have its own variables (attributes) and its own code (methods). This makes some things easier, particularly sharing data without resorting to lengthy function calls or messy global variables. It also effects a performance toll, though, and is quite tricky to get your head around. Very few languages are purely OO, although Ruby and Scala are exceptions.…

PHP used to stand for Personal Home Page, but these days it’s a recursive acronym for PHP: Hypertext Processor. Many of the world’s leading web applications, such as WordPress and OwnCloud, are written in PHP. It’s used extensively by some of the biggest websites in the world, some of which are so big (Facebook) that they had to write their own engine (HHVM) for it. Rather than using PHP in a traditional setting (running as a module through a webserver), let’s install PHP-CLI, the command line edition. This saves us the trouble of setting up Apache or some such (although that’s pretty easy nowadays, so you may want to do the tutorial this way and that is fine). On Debian-based distributions and their derivatives, you’ll want to run: Other distros…

Back in 2007 I started writing a blog on WordPress. I’ve been working professionally with the platform, and contributing code, since 2010. In this time, I’ve seen 17 major releases come and go. Still, nothing has excited me more, as a writer and as a developer, than the new feature set for WordPress 4.3. The core team announced the start of WordPress 4.0’s development at the end of April 2014. The 23rd release in its history, WordPress 4.0 was heralded as a landmark ‘.0’ release. It was led by a talented, UX-focused engineer and backed by hundreds of savvy developers across the globe. The initial slate of feature proposals was enough to excite every WordPress fan, and watching the update being narrowed down to a set of well-coded, well-tested, well-vetted…

WordPress has a gruelling release cycle, targeting a new version every four months. Getting stellar new features into WordPress core on such a limited timetable takes a lot of work, and requires a lot of community involvement. Want to get involved in the development of code for WordPress? The best way to do that and get up to speed is by following the core development blogs: WordPress Core (http://make.wordpress.org/core), WordPress UI Group (http://make.wordpress.org/ui) and WordPress Accessibility Group (http://make.wordpress.org/accessibility). It’s important to remember that even non-developers can contribute to ongoing development. Features need to be tested, bugs need to be reported and systems need to be documented. You can help build the next version of WordPress, even if you never write a single line of code. If you want to help…

I’ve coveredAmazon’s RDS MySQL service in the past, but this month an alternative came out of beta: Aurora. Announcedin2014, itisanother relational database option for AWS users, albeit with a difference. It promises up to five times the throughputof MySQL onthesamehardware, and is compatible with version 5.6 of the popular database engine. This is an internally developed RDBMS, though, by the sounds of things (details onany sharedcodebase with MySQL are hard to come by). Amazon is touting a zero downtime migration path for customers wanting to take the plunge. Beta testing, Amazon claims, shows thateach Aurora instance candeliverupto 100,000 writes and 500,000 reads per second, due it seems to tightly integrating the database engine with an SSD-backed virtualised storage layer purpose-built for database workloads. As well as the regular benefits of…

We’ve previously reported on the ability of the Raspberry Pi Foundation to expand its certification scheme to educators through the Google Digital Garage in Leeds. These have been so popular that Google has offered the foundation access to the Digital Garage in Birmingham. Picademy@Google is for classroom teachers of any subject at primary, secondary or post-16 level. The courses and workshops in Leeds are run by some chap called Les Pounder, who gives much of his time to helping adults and children create weird and wonderful projects. The new Picademy@Google Birmingham will offer all this good stuff with the help of some other chap called Martin O’Hanlon, renowned for his work related to stuffaboutrcode.com and Minecraft hacking, which we’ve featured in these very pages. If you’re interested in taking part…

Raspbian is based on the massively popular Debian distro, which means it has a plethora of commands. But what if you want to learn more about a command? Enter man , which is short for manual, a command used to access the help files for a command, eg to read the scrot, the screen capture tool, manual we would type: $ man scrot . This automatically opens the manual, which we can scroll through using the cursor keys, and exit by pressing q. Linux has another handy little trick: auto- completion. Commands entered into the LXTerminal/Bash can be auto-completed by pressing the Tab key, eg if we were to type scr followed by the Tab key, the word will auto-complete to scrot, if that’s not the command you’re looking for…

Our expert Nick Peers has 21 years of writing experience and has been dabbling with Ubuntu for years. His proudest achievement so far is his Minibianbased Raspberry Pi media server that runs Plex. LVM snapshot Set up a back up volume and use snapshots as a virtual test bed One of the most compelling reasons for implementing Logical Volume Management (LVM) on your hard drives is snapshots. If you’ve ever installed a buggy piece of software and then spent ages trying to undo the damage it’s caused, or had to sit back while you take a full backup of your hard drive before embarking on some testing, then snapshots will make your life so much easier. Snapshots are specially created volumes on your hard drive that help record the state…

Our expert Mihalis Tsoukalos is a programmer, mathematician and Unix and database admin, and when he’s not doing any of those four he’s an inveterate ‘doer of new things. Networking Testing TCP and UDP connections, using DNS-related tools Linux has a plethora of command-line tools that are related to networking. We’ll cover the most important ones that will help you identify and correct network-related problems. But as a general principle, always use the tool that you know best – provided, of course, that it’s suitable for the problem you are trying to solve. Usually, the most difficult part in the process is finding out where the problem is exactly and after finding out the root cause, the fix is generally a relatively easy task. Never forget to check your log…

Our expert Dr. Chris Brown provides Linux training, authoring and consultancy. He finds his Ph.D. in particle physics to be of no help in this work at all. This month we’ll turn our attention to signals. We’ll see what they are and meet some of the different signal types and their uses. We’ll see how to send signals from within our programs and how to write signal handlers that control how a program will react when it receives a signal. Finally, we’ll look at seven possible uses for signals. We were going to start with the OED’s definition of ‘signal’ but gave up when we discovered it runs to almost half a column. It’s a versatile word. In system programming terms, a signal is an event that’s delivered to a…

Our expert Kent Elchuk is a Canadian web developer who lives in Vancouver. In addition to developing custom, hand-coded websites, he’s the author of PHP/MySQL Fundamentals and Snippets and contributor to Codecanyon Marketplace. Have you ever wondered how some websites display combined data from various websites? This is a bit of trickery that can be done using a few methods, including having select database privileges from the sources, scraping data and using RSS feeds – or, in fact, any combination of these three methods. In this tutorial we’ll focus on how to retrieve and combine data from other sources using RSS feeds. RSS, which stands for Rich Site Summary (and later Really Simple Syndication), has been around a long time – and stems from Ramanathan V. Guha’s work at the…

This month we answer questions on: 1 Non-booting DVD distros 2 Lost email address book 3 Removing Xfce from Ubuntu 4 Converting DJVU files PDF 5 Fixing a slow hard drive * Repairing a broken bootloader 1 Unbootable Debian Q I cut my teeth on an 8-bit Sinclair ZX81. When I saw the 64-bit Debian 8 disk on the front cover of LXF199 I was keen to see the progress that has been made since then. I have a Viglen Genie, with an AMD Athlon 64 X2 Dual-Core Pro 4200+ running at 2.2GHz with a 32-bit Windows 7 OS. This assures me it’s 64-bit capable, but it won’t even look at the Debian distro. It won’t even load the elementary OS, but it has run the memory checker. Strangely enough,…

We often give a solution as commands to type in a terminal. While it is usually possible to do the same with a distro’s graphical tools, the differences between these mean that such solutions are very specific. The terminal commands are more flexible and, most importantly, can be used with all distributions. System configuration commands often have to be run as the superuser, often called root. There are two main ways of doing this, depending on your distro. Many, especially Ubuntu and its derivatives, prefix the command with sudo , which asks for the user password and sets up root privileges for the duration of the command only. Other distros use su , which requires the root password and gives full root access until you type logout. If your distro…

We receive several questions each month that we are unable to answer, because they give insufficient detail about the problem. In order to give the best answers to your questions, we need to know as much as possible. If you get an error message, please tell us the exact message and precisely what you did to invoke it. If you have a hardware problem, let us know about the hardware. If Linux is already running, you can use the Hardinfo program (http://bit.ly/Hardinfo) that gives a full report on your hardware and system as an HTML file you can send us. Alternatively, the output from lshw is just as useful (http://ezix.org/project/wiki/HardwareLiSter). One or both of these should be in your distro’s repositories. If you are unwilling, or unable, to install these,…

You get an education! You get an education! You get an education! It’s not something Opera would give away, as I guess to some a free car would seem more valuable, but how much is an education worth? I’d suggest on a purely practical level a huge amount, and we all know it’s something that’s truly invaluable. It’s one part of FOSS that we almost take for granted, but by providing the tools and documentation it’s assumed that people can and do educate themselves in everything they need to know. So what happens when you take those tools and documentation and give them to education professionals? In 2015 the UK is going to find out, as it’s the first year when the new computing curriculum kicks in. This is the…

Security researchers Runa Sandvik and Michael Auger have developed a technique to hack, via the WiFi connection, a well-known Linux-powered rifle. This enables them to disable or even change target on the fly. The rifle uses its on-board computer to adjust for the bullet weight, wind and other environmental factors to ensure an inexperienced shooter can hit targets up to a mile away. See the YouTube video for more: http://bit.ly/LXF202hack. This follows similar scary revelations of cars being hacked and forced to a stop. Though many do point out this requires the hackers to have prior physical access to the car. Find out more details: http://bit.ly/LXF202stop…

Bristol and Bath LUG Meet on the fourth Saturday of each month at the Knights Templar (near Temple Meads Station) at 12.30pm until 4pm. www.bristol.lug.org.uk Edinburgh LUG First Thursday of the month at the Southsider pub, West Richmond St, Edinburgh. www.edlug.org.uk Hull LUG Meet at 8pm in Hartleys Bar, Newland Ave, first Tuesday of every month. http://hulllug.org Lincoln LUG Third Wednesday of the month at 7.00pm, Lincoln Bowl, Washingborough Road, LN4 1EF. www.lincoln.lug.org.uk Liverpool LUG First Wednesday of the month from 7pm onwards at DoES, Hanover St, Liverpool. http://liv.lug.org.uk/wiki Manchester Hackspace Open night every Wednesday at its space at 42 Edge St, in the Northern Quarter of Manchester. http://hacman.org.uk Preston Raspberry Jam Meet the first Monday of each month at UCLAN Media Innovation Studio. Visit website for the next event.…

Firstly, thank you for an excellent and class magazine. While I can empathise somewhat with Mr Hockin on his wider points about Linux “wizards”, my personal Linux journey has been much more rewarding and gratifying. A thank you very much to LXF. I have a technical background, but I am by no means a Linux guru or expert and sometimes I struggle with some of the magazine content. Having said that, my most satisfying achievement is to have encouraged over 30 newbies to try Linux. I am glad to tell you that all of them, bar five or six continue using Linux for their daily PC chores. All of these newbies are non-technical man/woman-in-the-street users, who regard the PC as a tool to manage their everyday tasks. A common theme…

Chromebooks are by definition online machines designed to hook up to the cloud, so with that in mind it’s imperative that these beasts come with rock-solid wireless connectivity. We’d also expect to have Bluetooth support out of the box – how else are you going to enjoy a bit of White Snake while coding your Python and not disturbing the tranquillity of your local library? Starting at the top of the pile, the Chromebook Pixel offers dual-band Wireless AC via the Intel 7260 Wi-Fi card and Bluetooth 4.0LE, but most impressively it also packs in two USB-C ports and two USB 2.0 ports, which frankly covers everything you’re likely to need for the foreseeable future. The Flip is also impressive in this area with wireless AC, Bluetooth 4.1 and micro…

This is going to be a very gentle introduction to programming in Python in which we’ll explore the basics of the language, then use the Pygame module to make a simple game. That we are able to do this is testament to the power of Python and Pygame: much of the tedium inherent in game work is abstracted away and, once we’ve covered some elementary programming constructions, for the most part we work with intuitive commands. First follow the instructions in the box to check which version of Python you have and install Pygame. Whether you’re on a Raspberry Pi or a larger machine, start at the command line. So open up a terminal (LXTerminal in Raspbian) and start Python 2.7 with Alternatively, start up IDLE and start a command…

Part of Key Stage 2 involves learning to understand and program simple algorithms. We’ve already covered our basic gameflow algorithm – wait for a mouseclick (or for the user to quit), check if that’s a valid move, check if there’s a line of five, etc. At the heart of that last stage, lies a naïve, but nonetheless relevant, algorithm for detecting whether a move is a winning one. Consider the simpler case where we’re interested only in horizontal lines. Then we would loop over first the rows and then the columns of our grid array. For each element we would check to see that it is non-zero (i.e. there is a counter there) and if the four elements to its right have the same value. In Python it would look…

In September 2014, the UK embarked on a trailblazing effort which saw coding instilled in the National Curriculum. When the initiative was announced in 2013, then education secretary Michael Gove acknowledged that the current ICT curriculum was obsolete – “about as much use as teaching children to send a telex or travel in a zeppelin”. Far more important was imparting coding wisdom unto the young padewans. Coding skills are much sought-after, as evidenced by industry consistently reporting difficulties in finding suitably qualified applicants for tech jobs n the UK. The ‘Year of Code’ was launched to much fanfare, though this was slightly quelled as details emerged: a mere pittance was to be added to the existing ICT allocation, and most of this would be spent on training a mere 400…

Programmers are very keen on writing efficient code. This is not just because they like elegance (though as a rule they do); as we’ve mentioned, inefficient code might be fine to begin with but can start running as slow as treacle when asked to deal with heavier loads. Here we can use a smarter Fibonacci function which passes the two previous numbers in the sequence, so that no effort is wasted. But we still want to be able to call our function with a single argument, so we’ll make these extra arguments optional, setting their defaults to 1 and 0: Besides defining our new improved function fib2() we also use the special variable $argv to allow the user to provide input on the command line. If one saved this file…

After the second beta release, I had the opportunity to sit down with Helen Hou-Sandi, the release lead for WordPress 4.0, to learn a little more detail on how she’d seen the project evolve over the past few months. Past versions of WordPress platform often had themes for their release to guide the overall development of the project. Version 4.0, however, had less of a central theme:“We’ve been better at iterating on what we’ve already got ” Hou-Sandi explained. As a result, most of the features scheduled for the release had been built on past successes or focused on refreshing elements. An example of the latter is the WordPress plugin interface. According to Hou-Sandi, plugins are “central to what WordPress can do”, but the interface has remained relatively untouched since…

Anyone who has had to deal with a system that handles credit card information will know of PCIDSS – the Payment Card Industry Data Security Standard. This is a series of best practices and security controls designed to prevent credit card fraud. It introduces controls around data and reduces its exposure to compromise. However many of the practices are applicable to all systems that store customer data, and anyone designing such a system would do well to review it (boring as that may sound). A lot of the contents are common sense to sysadmins (and I think deliberately rather vague in some cases) – building a secure network, for example, or regular testing and monitoring being required. Companies at the higher classification end of the PCI spectrum – usually large…

The Pi is helping people all around the world solve problems by putting a tiny PC where none has gone before. One project uses a Pi to create a low-cost hydrophone (underwater microphone) to record and track cetaceans in the oceans. Commercial units are prohibitively expensive and generally can’t be modified. The project team tested their autonomous recorders off the coast of Brazil, monitoring marine traffic and whale and dolphin populations. With the maximum five battery packs, a device could deliver almost two weeks of continuous recording. http://bit.ly/LXFhydrophone…

Our expert Les Pounder has been hacking the Pi for three years and is part of the Raspberry Pi Foundation’s Picademy team training teachers. He blogs at http://bigl.es Raspbian has been the default distribution (distro) for the Raspberry Pi since its launch in 2012. In this time we’ve seen the distro grow from a simple fork of Debian into a fully featured product that covers many different use cases. In this tutorial we peek under the hood and get to know the latest version. The easiest way to install Raspbian is via NOOBS (New Out Of the Box Software). For this you will need at least an 8GB micro SD card that’s formatted to use a FAT32 filesystem. Download the NOOBS ZIParchive (www.raspberrypi.org/downloads) to another computer and extract the contents…

Our expert Mayank Sharma was a contributing editor for www.linux.com and has written for Linux Today, Digg and PC Plus. Do you use the Raspberry Pi for a headless project, such as a media player, NAS server, seed box or security camera? If you do, then your Pi is probably tucked away somewhere that’s not that easily accessible. You can always log in to it remotely but how do you monitor it in real time? How do you know whether it’s overheating? Or running out of disk space? In this project, we’ll play God and make your Raspberry Pi self-aware, and give it the ability to communicate. Inmore earthlyterms, we’llinstallthe sendxmpp toolon the Raspberry Pi, which allows it to communicate via the popular XMPP messaging protocol. We will use this…

One of the trickiest things to manage with snapshot volumes is their size. If you have a large hard drive, then allocating more than you think you’ll ever need is easy enough, but what if you’re pressed for space? The problem is, if you allocate too little to your snapshot volume and it fills up with all the changes you subsequently make, the snapshot is rendered invalid and you can’t use it - even to restore your system from that point. If you have enough free unused space you can resize the volume before it’s full up, ensuring it continues to work properly. This can be done manually using Logical Volume Manager by selectinh your snapshot volume under ‘Logical View’ and clicking ‘Edit Properties’ to extend it. It’s also technically…

Our expert Neil Bothwick has a great deal of experience with booting up, as he has a computer in every room, but not as much with rebooting since he made the switch to Linux. Networking Use ZeroTier to set up secure private networks quickly AVPN is considered the best option, if you want to connect to your network from the outside in a secure way. We’ve looked at setting up OpenVPN in the past, but it’s not a trivial task. Both setting up the VPN server in the first place and managing changes when devices are added or moved can be time consuming. It would be great if someone were to give us an alternative that was easy to set up and manage, preferably with a simple web interface –…

All systems and network administrators know how important it is to have a high-level view of network traffic, both for security and network monitoring purposes. As network data flow is getting bigger and bigger, it’s very difficult to watch all the data all the time. Therefore, you need a way to get a quick overview of your network data. We’ve generated a plot (see bottom, p81) in R using the following commands: The graph visualises the frame.time_relative value, which is the time offset from the first packet. This gives you a good indication of your network traffic flow. Statistics can be very helpful when you have to deal with lots of data but this could be the subject of a separate article.…

Our expert Neil Mohr has been hacking tablets since the HP TouchPad running the open source WebOS, but we won’t mention his time owning a first-gen iPod touch. Ubuntu Touch Prepare and back up a Nexus device and flash Ubuntu onto it Part of the plan for Ubuntu is to have it running everywhere and on everything. This is called convergence, and even Microsoft is embracing it with Windows 10. Part of convergence is that Ubuntu and its desktop have been built to be adaptable, so the interface can scale from large 4K desktop displays down to small ultraportable laptops, and even squeezes onto tiny phone screens with touch input. This means that if you own the right tablet, you can dump Android and install a full Linux desktop with…

The ‘HUP’ of SIGHUP stands for ‘hang up, and is deserving of an explanation. Early telephones (long before even my memory) had a hook on the side and to end the call you would simply hang the receiver back on the hook. We still use the expression: “He hung up on me!” even with the hooks long gone. Anyway, suppose Ken was logged in to his Unix system via a modem and phone line (the usual way to get remote access before IP connectivity came along). He was running a shell when, for whatever reason, he ‘hung up’ the connection. Later, Dennis logs in to the same modem and finds himself talking to Ken’s old shell. Not good. To avoid this situation, the modem and its device driver conspire together…

Since the output is displayed in a basic table, it currently doesn’t look that stylish, but you could easily add a plugin that will do the job of smarting up your output. If you do a web search for ‘best responsive bootstrap table plugins’ you will see that there are many options and tutorials for adding styles, but we’ll quickly explain how to using a plugin called Datatables, which can be downloaded at https://datatables.net/download/download. Not only will Datatables provide a resizing table for many devices and is searchable, you can also select how many entries you want to see on a page. Although we’ve provided a file called index_ styled.php on the LXFDVD, I will quickly explain how easy it is to add the plugin. The first step is to go…

Linux Format is proud to produce the biggest and best magazine that we can. A rough word count of LXF193 showed it had 55,242 words. That’s a few thousand more than Animal Farm and Kafka’s The Metamorphosis combined, but with way more Linux, coding and free software (but hopefully less bugs). That’s more than most of our competitors, and as for the best, well… that’s a subjective claim, but we do sell way more copies than any of our competition in the UK. As we like giving things to our readers, each issue the Star Question will win a copy of one of our amazing Guru Guides or Made Simple books, discover the full range at: http://bit.ly/LXFspecials For a chance to win, email a question to lxf.answers@futurenet.com, or post it…

* Broken bootloader Q I have an old Windows XP laptop on which, a number of years ago, I installed Linux Mint 8. Yes, I said it’s old! I now want to upgrade to Mint 15 for which I have the install disk. I’ve reformatted the old partition containing Mint 8, in preparation for replacing it. However, now when I reboot the laptop, Grub gives me a message Error 17 and it appears I can’t re-attempt the boot from this point. I suspect I shouldn’t have deleted the partition containing the first option in the boot list – how do I get out of this problem please? I don’t have a rescue disk for the Windows XP even if the laptop’s dual-boot mechanism would let me use it, and I’m…

Recently, I watched a TV show about dogs that told us all dogs – from Great Danes to Pugs – are descended from one breed of wolf. I was amazed that in just a few thousand years so much diversity had occurred from a single source. I was reminded of this when compiling this Linux Format DVD. We have two distros based on Ubuntu, which share a common ancestor but appear so different. The third distro, OpenMediaVault, is even more distinct but is based on Debian, so all three distros share a grandparent. It shows the truth of the saying ‘Linux is Linux’: these distros all share the same basic kernel code, and very much more besides, but they look and feel so different. Being able to change so many…

Canonical has revised its legal policy dealing with intellectual property in Ubuntu (see http://bit.ly/LXF202-ubuntu-ip) and it’s causing quite an uproar as it could fundamentally change how easy it is to distribute Ubuntu or Ubuntu-based distros in the future. The passage causing most concern states: “any redistribution of modified versions of Ubuntu must be approved, certified or provided by Canonical if you are going to associate it with the Trademarks. Otherwise you must remove and replace the Trademarks and will need to recompile the source code to create your own binaries” Canonical sees this as making sure people don’t modify Ubuntu and then pass it off as an official Ubuntu release, but the implications go much further. Matthew Garrett says in a blog (http://mjg59.dreamwidth.org/35969.html): “[on] a strict reading of the policy,…

A bug has been discovered in Samsung SSDs and the way they implement TRIM. A Samsung report suggests the bug is caused by the Linux kernel. RAID implementations in Linux use separate buffers in memory for each sequence of read or write operations, but with TRIM a single shared buffer is used. A bug could result in race conditions meaning TRIM commands making use of the shared buffer could get confused. Samsung has developed a fix and a workaround patch has been developed and committed to the kernel source tree. If you have a linear, RAID 0 or RAID 10 configuration using Samsung SATA SSDs it’s advised that you disable TRIM altogether until a kernel version is released that includes the patch. Even more games are coming to Linux! Classic…

ExTIX ExTiX 15.3 LXQt is the latest release of the Ubuntu-based distribution that bills itself as “The Ultimate Linux System” and comes with the fast and lightweight LXQt desktop environment, which was created by the merge of LXDE-Qt and the Razor-qt projects. The 64-bit distro is based on Debian 8.1 Jessie/Ubuntu 15.04. LibreOffice, Thunderbird, GParted, Brasero, SMPlayer, and GCC are some of the packages included, and Chrome is the default web browser rather than Firefox. Find out more about the latest release at http:// www.extix.se. SLACKEL 4.14.3 Slackel is a distribution based on Slackware and Salix, and the latest version is now available for download. It comes with the 3.18.11 kernel, supports 32-bit and 64-bit x86 builds and can boot on UEFI-enabled devices – though Secure Boot is not supported. The…

Over the Air 25-26 September sees the return of Over the Air, an event that looks to the future of mobile technology, languages and their API and the rising trend in open hardware. Over the Air uses a mix of show-and-tell sessions, workshops and lightning talks to entertain and inform attendees. But along with the talks is a 36-hour hackathon for those who want to get their hands on the latest in mobile technologies. http://overtheair.org/blog Oggcamp 15 The team are beavering away to finalise the venue but they can confirm that this year sees the return of the Open Hardware Jam, which was last seen at Oggcamp 12. The Jam will be organised by the Liverpool Make Fest team, who attracted over 2,000 people to their recent event. So an…

Specs OS: Android 5.0 CPU: Intel Atom Z3580 quad-core 2.3GHz RAM: 2GB Display: 10.5-inch 1,600x2,560 GPU: PowerVR G6430 Storage: 32GB Cameras: 8MP and 2MP Comms: Wi-Fi 802.11a/b/g/n/ac, Bluetooth 4.0, GPS Battery: Up to 7 hours, 7,000mAh Size: 243.4x 195.4x6.2mm From the Nexus 9 to the Lenovo Yoga Tablet 2, there have been many attempts to create a productivity minded Android device. You can’t blame manufacturers for trying. After all, the promise of a device that can be both your mobile movie screen and your on-the-go office is enticing. The Venue 10 7000 is one such device from Dell and as part of Dell’s premium 7000 line, this 10.5-inch slate is a cut above your typical Android tablet, with a 2,560x1,600 OLED display. What’s more, a quad-core, 2.3GHz Intel Atom Z3580…

Chromebooks aren’t the only fruit in the mobile market, but when it comes to Linux the options are pretty limited. In terms of other Chromebooks there is the Toshiba Chromebook 2 and on the horizon is a high-end Acer Chromebook C910, which will sport a similar specification to the Google Pixel 2015. Outside of the burgeoning world of Chromebooks you could opt for a more ambitious Android device, such as the Dell Venue 10 7000 (see Reviews, p17) but Android simply isn’t set to be a true multitasking system, yet. We always find that working on Android feels like a compromise and the devices themselves don’t always work as well as they should. Full Linux laptop options are still sadly limited: we’ve seen individual stores such as Ebuyer offering the…

If you’re using Raspbian on the Raspberry Pi or any flavour of desktop Linux, then the chances are that you already have at least one (probably two) versions of Python installed. While the latest release (1.9.2) is now Python 3 compatible, no distributions are shipping this version yet, so we’ll stick to Python 2 (2.7 to be precise) for this tutorial. Check your default Python version by typing: If this returns a result that begins with 2, then everything is fine. If, on the other hand, you see 3-point-something, then check Python 2 availability with the command: Some distros, notably Arch Linux and the recently released Fedora 22, don’t ship the 2.7 series by default. Installing Pygame, however, will pull it in as a dependency, so let’s do that now.…

One of technology’s greatest achievements was IBM’s Fortran compiler back in the 1950s. It allowed computers to be programmed using something a bit less awkward than machine code. Fortran is still widely used today and, while some scoff at this dinosaur, it remains highly relevant, particularly for scientific computing. That said, nobody is going to start learning it out of choice, and there are all manner of other languages out there. Traditionally, you have had the choice between hard and fast languages – such as Java, C and C++ – or easy and slower ones, like Python or PHP. The fast languages tend to be the compiled ones, where code has to be compiled to machine code before it can be run. Dynamic languages are converted to machine code on…

There are also over 2,000 volunteer-run code clubs across the UK. Code Club, armed with £100,000 courtesy of Google, provides the material, and schools (or other kind venues) provide space and resources for this noble extracurricular activity. The Code Club syllabus is aimed at 9-11 year olds and consists of two terms of Scratch programming, then a term of web design (HTML and CSS), concluding with a final term of grown-up Python coding. Projects are carefully designed to keep kids interested: they’ll be catching ghosts and racing boats in Scratch, and doing the funky Turtle and keeping tabs on the latest Pokémon creatures in Python, to name but a few. If you have the time and some knowledge, it’s well worth volunteering as an instructor. All the tutorials are prepared…

WordPress 4.0 “Benny” was released 4th September 2014 and the team ever since then has been steadily releasing point updates, with the most recent being 4.3 in August 2015. Here’s a rundown of the biggest new features that have been added over the last year: WordPress 4.1 “Dinah” – December 2014 New core theme – Twenty Fifteen Distraction-free editor mode In-line image editing toolbar Log out from everywhere Vine support was added WordPress 4.2 “Powell” – April 2015 New Press This publishing shortcut system Extended character support Instant theme switching Tumblr and Kickstarter embedding Streamlined plug-in updates WordPress 4.3 “TBC” – August 2015 New navigation menu editor Create your own Favicon Stronger password creation New text formatting shortcuts Full Press This editor…

Now, I don’t know about anyone else, but I don’t think there has ever been a better time to be working as a sysadmin. There are challenges to face, to be sure, such as the rate of technological change – in my career span I’ve gone from looking after every single component of a server and all its associated power/cabling etc to not actually even knowing (or caring) where my systems reside. There are also still market forces which undervalue the sysadmin skill set. The stereotype of the underpaid, vastly overworked sysadmin still exists. (My advice: leave that job and get another one!) But generally, I much prefer working in today’s environment than the ‘good old days. Remote working is commonplace. The rise of DevOps as a culture and job…

Anyone who collects movies and pictures on their system hard drive will soon be thinking about upgrading to NAS (Network-Attached Storage), and although it may sound complicated it’s not thanks to OpenMediaVault, a dedicated solution that tackles the problem easily. OpenMediaVault is a specialised Linux distribution (distro), which is based on GNU/Debian and features SSH, (S)FTP, SMB/CIFS, DAAPmedia server, rsync, BitTorrent client and all the components required for turning your device into a NAS. OpenMediaVault is generally for use in a home or small office setting, which means that you can install it onto an old PC and not necessarily a powerhouse. In fact, OpenMediaVault can even be run inside a virtual box, as you forward an external storage device from the host system to the guest. The deployed system…

Two years ago I was teaching an introduction to Raspberry Pi in a local primary school. Even with a small group of students, it was a logistical nightmare. I had to build a perfect SD card image with all the software needed and flash it onto an SD, which took hours. One card failed, I had to get the students to all install a piece of software I forgot, and I mixed up the SD cards a number of times. This experience got me thinking: there must be a better way… I had at the time been playing with LTSP (Linux Terminal Server Project), which was built to help schools set up and maintain a classroom of Linux machines. I quickly discovered that getting it working with Raspbian would be…

The much loved community born Pi supplier Pimoroni turned three-years old in August. It’s moved to larger premises and employs 20 people. To celebrate this milestone, Pimoroni decided to dust off its Picade Kickstarter project and give it a new lick of paint. The stylish, self-assembly retro arcade cabinet for your Pi features a new PCB (Arduino compatible with stereo 2.8W amplifier), a proper arcade joystick and 12 micro-switch arcade buttons. It’s a touch pricey at £180 but the smaller Console version comes in at £90, which includes HDMI output. http://shop.pimoroni.com/products/picade…

The Raspberry Pi has its own configuration tool, raspi-config. In the tutorial, it opened automatically when we first booted the Pi. But should you need to make any further changes you can also re-open it from the LXTerminal by typing $ sudo raspi-config . Using raspi-config we can enable the official Raspberry Pi camera, configure audio and SSH server to run at boot. We can also overclock our Pi to force it to run faster, but this can damage your Pi if you push it too hard. Overclocking the CPU generates a lot of heat and the Pi doesn’t come with a heatsink to dissipate CPU heat. Raspi-config can also be used to change the memory split between the system and the GPU (Graphical Processing Unit), eg a web server…

At this point, you may be wondering about ZeroTier’s servers – are there any disadvantages to using a system that has a public discovery server? While its servers could be compromised, the code is visible, which means it’s up to you to decide how much you trust it. The service is free, but limited to ten computers per network, although it appears you can create as many networks as you want. If you want more than ten users on a network, you can pay $4 per month or you can run your own server, which also means you have full control over your data. The binary packages don’t include the server, so download and unpack the source and run: This compiles the zerotier-one program with network controller support and then…

Nmap is an open source tool, created by Gordon Fyodor Lyon, that supports port scanning, operating system detection and version detection. Although regular users can perform various Nmap scans, particular command line options demand root privileges to run. Nmap canhelpyou recognise the type of network device and the services that it runs. You can also tell if you can communicate with the remote device. If you want to ping multiple devices at once, you can always execute a ping scanusing Nmap: nmap -sP 192.168.1.0/24 . The command nmap -sU aMachine will also perform a UPD port scan on a machine (called aMachine).…

At this stage, Ubuntu Touch runs perfectly but has few apps to offer outside of an excellent browser. This means you’ll want Android back. To do this on your Ubuntu desktop, download the correct Android image for your device. The full list is here: http://bit.ly/1M3PrCr. You need to cd to the Download folder and then type tar -xzf <archivename> . Then type cd <archive folder> to enter the new directory. Remember you can use ls to list everything in the current directory. Connect your Nexus device to the Ubuntu desktop, and type the following to first check that it’s connected, reboot into the bootloader and then flash the Android image: Wait until Android boots to its welcome page. If you’ve previously made a backup, as we suggested, you can restore…

If you’ve been following this series you’ll know that a program that terminates of its own free will return an exit status – a small integer – to its parent, with 0 indicating a normal, successful exit and non-zero values indicating some kind of failure. But a process terminated by a signal doesn’t get a chance to specify an exit status. In this case, the lower byte of the status retrieved by a wait() call will contain the number of the signal that caused termination. The following code illustrates the use of four macros: Here we see that if the child terminated normally, WIFEXITED returns true and WEXITSTATUS returns its exit status; if the child was terminated by a signal, WIFSIGNALED returns true and WTERMSIG returns the signal number. It…

Scraping is an alternative method to using if an RSS feed if one isn’t available. This is a technique where source code from a web page is analysed for patterns of data that you might be interested in. Some of your sources may not supply RSS feeds. But, since they likely provide some kind of listings using HTML web page lists, tables or ordered <div> tags, you can always look at the source code, find the relevant pattern and then scrape the data out. Often, entries of this kind will have a unique class or some other set of attributes that can make it easy to identify a beginning and end to the useful data. To scrape a page with PHP, you can use one of its functions, such as…

Nothing is more infuriating than random crashes of a computer. If a crash is reproducible, you have a starting point to investigate, but if it happens at any time and using any software where do you look? If it happens regardless of the software you’re using, it may be a hardware problem. If you have a spare PSU, try swapping your current one out. Desktop PSUs can vary greatly in quality and the cheaper ones can cause the sort of power glitches that will crash a computer. They can also damage components that cost several times more than a new PSU. If it’s a laptop, the battery may be on the way out. If the computer doesn’t run reliably on battery power alone, look for a new battery. The other…

Most of the time you can get all the software you need from your distro’s package repositories (repos). Even if the core repos don’t have what you need there’s often a package in an external repos, such as an Ubuntu PPA, that you can add to your package manager’s list of sources. There are times that you can’t get what you need from your package manager, either because the software you want hasn’t been packaged for your distro or you need a feature from a version later than the one your distro provides. In those cases, it’s time to roll your sleeves up and compile from source, which is nowhere near as scary as it sounds. You don’t need to know how to program, the software has already been written,…